URI WG minutes

Daniel LaLiberte (liberte@ncsa.uiuc.edu)
Fri, 21 Apr 95 09:44:58 CDT


Date: Fri, 21 Apr 95 09:44:58 CDT
From: liberte@ncsa.uiuc.edu (Daniel LaLiberte)
Message-Id: <9504211444.AA22862@void.ncsa.uiuc.edu>
To: Larry Masinter <masinter@parc.xerox.com>
Cc: uri@bunyip.com
Subject: URI WG minutes
In-Reply-To: <95Apr20.181834pdt.2761@golden.parc.xerox.com>

Larry Masinter writes:
 > Minutes of Uniform Resources Identifiers Working Group, April 3 & 4,
 > 1995. 

 > * Michael Shapiro presented the Path URN scheme.
 >   - Totally separate from hostnames, but have to emulate what DNS 
 >     is doing now.

This is potentially confusing.  The idea is that if the path scheme
does not use DNS for its implementation, we would have to recreate the
features of DNS used by the path scheme.

 > 6. The remainder of the session was given over to continued discussion
 > of the 5 URL schemes and associated issues.
 > 
 > * Most of the URN schemes don't really go into details about what
 > happens when something moves.  So far have dealt only with what
 > happens when a whole organization moves.  Granularity of mobility must
 > be addressed.

The description of the path scheme should have made it clear that the
path scheme does allow fine grain mobility.  There are two mechanisms
to support this, one for directories and one for individual documents.
If a subdirectory of documents is moved to a new server, the
resolution process for looking up a name of one of those documents
will find the new server because it is more specific.  (Name servers
near the client can cache the location of the new server.) If just a
single document is moved, the original server would forward references
to the current location.

 >        For example:
 >
 > - All web documents from CERN move to INRIA, but high-energy physics
 >   documents stay at CERN. What happens to URNs for the web documents?

Depending on how the documents are layed out (how they are named) this
would probably be handled by the first mechanism that supports
subdirectory relocation.

 > - A grad-student graduates but someone wants to retain editorial
 >   control of one of his pages. How can this happen?

If the someone who wants to retain editorial control of the page is
associated with the original server, then the student should agree to
forward requests of the page back to the original server in exchange
for the original server agreeing to forward requests for all the
student's documents to the new server.  Perhaps the original server
should never have given the student control of such a document in the
first place if it planned to retain control.  Perhaps a flat name
system could handle these change of control issues better.

The path scheme could have a mechanism to essentially appeal to a
higher authority, in case the immediate parent authority doesn't want
to cooperate.  Perhaps the path scheme already allows this appeal
process - have to think about it some more.  This is where the
hierarchical path scheme starts to merge with the centralized handle
scheme.

 > - A university retains all articles by staff members; someone on the
 >   staff publishes the exact document in an online journal.  Does it
 >   get a new URN, or just keep the old one?

This is a question not about mobility but about the abstraction of
names of things that are replicated.  Each of the university copy and
the online journal copy could have individual URNs, and another URN
could be assigned to the abstraction over both.  Caches should use the
more abstract URN, unless there is something to distinguish each of the
copies, such as the online journal copy costs more.

 > * Are we trying to solve NIDR with permanent names?  Names should last
 > as long as the issuing agency...  go to a permanent naming authority
 > if you want your stuff to last.

Or the resolution of new names could be controlled by issuing agency
as in the path scheme, but the resolution of old but still valuable
names could migrate up to a permanent central resolution service.

 > * Some assert that it's time to decide on a syntax and character set
 > so experimental work can go forward. On the other hand, we must agree
 > on the semantics before we do a syntax.

There is no point in considering a common syntax across all URNs
(other than the generic URL syntax) unless it makes sense to have a
common semantics across all URNs.  I don't believe it makes sense to
think that we can come up with a common semantics for all possible
name schemes, now existing or created in the future.  The generic URL
syntax allows any semantics, and that is what we need in general.

Daniel LaLiberte (liberte@ncsa.uiuc.edu)
National Center for Supercomputing Applications
http://union.ncsa.uiuc.edu/~liberte/